EEPORT OX THE ECHINOIDEA. 155 



between the Pourtalesise proper and such genera as Pdleopneustes and PalcBOtropus, in 

 which the actinostome is more or less labiate, and in which the structure of the actinal 

 surface resembles more closely that of the normal Spatangoids. Cahjmne has, like the 

 Pourtalesise, simple ambulacral pores, a disconnected apical system retaining something 

 also of its cylindrical shape ; two of the ovaries in the trivium, the others not developed, 

 the bivium well separated from it by intercalated interambulacral plates. It has a simple 

 actinostome, and large ambulacral plates ; the proportion between the size of the 

 ambulacral and interambulacral plates is similar to that in Cystechinus. It has, unlike 

 the Pourtalesise proper, an elliptical outline and a fasciole across the anterior edge of the 

 test. The median interambulacral area of the actinal side forms a narrow rounded keel 

 extending from the edge of the actinostome to the ambitus, but like Cystechinus a nearly 

 flat actinal surface with a low rounded keel extending almost from the actinostome to the 

 posterior edge of the test, where it runs into a small but well-defined subanal beak, the 

 only remnant in this genus of the anal snout of the Pourtalesiaj proper. The presence of 

 so well-defined a lateral fasciole in this genus is interesting, as otherwise the genus is 

 eminently an old type, but combining with its ancient characteristics such as the uniform 

 size of the coronal plates of the test on the abactinal surface, a disconnected apical system, 

 a simple actinostome with the remarkably simple arrangement of the plates imLmediately 

 surrounding it and a short elliptical outline, the more modern features of a distinct sub- 

 anal beak, a lateral fasciole, an anal system high upon the posterior extremity of the test 

 close to the abactinal surface, and an elongated actinal plastron with a well-defined 

 lateral fasciole. 



When seen in profile this genus retains of the Pourtalesise the cylindrical shape and 

 the actinal surface slightly convex from the presence of a keel ; and by the position and 

 structure of its anal system it unites the Spatangina and the PourtalesiaB l:)y showing the 

 connection of Calymne to Urechinus, Cystechinus, Echinocrepis, and Pourtalesia proper, 

 in addition to such features as the presence of a lateral fasciole to which I have already 

 alluded. The general outlines of the test recall on the one side the Ananchytidse and on 

 the other the Dysasteridse, and even some of the Clyi^eastroids, and resemble to a very 

 striking degree those of the test of young specimens of Cystechinus. 



""Calymne relicta (Pis. XXXIV., XXXIX. figs. 24-26; PI. XL. figs. 63-65; 

 PI. XLIII. fig. 24 ; PL XLIV. figs. 47, 48). 



Calymne relicta, Wy. Tliomson, 1877, Voy. Chall, Atlantic, vol. i. p. 397, figs. 102, 103. 



Only fragments of this species were preserved, from which, in connection with the 

 drawings given by Thomson in the Challenger narrative, the figures on Plate XXXIY. have 

 been reconstructed. I copy Thomson's description of this species (Voyage of the Challenger, 

 Atlantic, vol. i. p. 397). " The test is 30 mm. in length and 20 mm. in height, and 

 very elegant and symmetrical in form ; the outline is oval, slightly truncated posteriorly, 



